1. Field of the Invention
The present invention relates to a digital type image forming apparatus, and more particularly to a digital type image forming apparatus, such as a digital copying machine, a facsimile machine, and so forth, which is capable of handling simultaneously input data without causing a delay.
2. Discussion of the Background
In general, an image memory for storing image data has been an important component of a digital type image forming apparatus, such as a digital copying machine, a facsimile machine, and so forth. For example, a digital copying machine which generates image data by reading an original document can store the image data in an image memory so as to be able to manipulate such image data stored therein, using various image editing functions at a later time. The image editing functions of the digital copying machine includes an electronic sort function, a combining function, and the like. The electronic sort function changes a sequence of images based on the image data stored in the image memory and outputs the images in a changed sequence. The combining function combines a plurality of images stored in the image memory into one image and outputs the combined image.
In order to sufficiently perform these image editing functions, the digital copying machine is required to have an image memory which is capable of storing a large amount of image data and processing the image data at a relatively high speed. To cope with these requirements, some digital copying machines use two memory units.
Typically, a first memory unit uses a DRAM (Dynamic Random Access Memory) that enables a relatively high speed read/write access so that read/write operations can be performed in approximate synchronism with a relatively high input/output data rate of the image data. Also, a second memory unit typically uses a HDD (Hard Disk Drive) that is capable of storing a large amount of data so that various image editing functions, including the electronic sort and combining functions, can be performed without causing a problem of insufficient memory capacity.
On the other hand, the digital copying machine is integrated with various functions, such as a printing function for printing an image based on the image data which is output from an external device. Such an integrated digital copying machine which is capable of performing both printing and copying functions includes separate data paths for the image data generated by a copying operation and for the image data received from an external source for a printing operation.
When such an integrated digital copying machine activates both copying and printing operations at the same time, both operations generate image data and transmit the image data to the respective data paths at the same time. In this case, however, in one of these two operations the timing of storing the image data into the image memory is delayed since the memory only allows one access at a time. As a result, and as shown in FIG. 9, the image data of the copying and printing operations will be stored in first and second memory units in an alternate sequence. FIG. 9 shows a time chart for explaining an operation in a background digital copying machine for loading image data for copying and printing operations into first and second memory units, using two data input paths 101 and 102.
Therefore, the background digital type image forming apparatus does not allow simultaneous memory accesses to an image memory thereof for input and/or output by more than one resource of image data.
In light of the above noted and other problems, an object of the present invention is to provide a novel method and apparatus for forming an image, which is capable of handling simultaneously input data without causing a delay.
These and other objects are achieved by a novel image forming apparatus of the present invention which includes a plurality of memory devices, each including at least one image memory which stores image data. A controller controls input and output operations for the image data relative to the at least one image memory. An image reading device generates the image data by scanning and reading an original document. At least one data input device inputs image data generated by an external source. A plurality of input paths transmit the image data generated by the image reading device and the image data input by the at least one data input device. An image memory switching device connects the plurality of input paths to the plurality of memory devices, receives the image data generated by the image reading device and the image data input by the at least one data input device, and switches the plurality of memory devices to transmit consecutive image data, which is consecutively sent through one of the plurality of input paths, to a same memory device among the plurality of memory devices when the image memory switching device receives the image data and the image data through the plurality of input paths.
The image memory switching device switches among the plurality of memory devices to transmit consecutive image data generated by a same function to a same memory device among the plurality of memory devices when the same memory device among the plurality of memory devices stores the image data which is generated by the same function.
The image forming apparatus may further include an image printing device which prints an image on printing paper based on the image data stored in the image memory according to an electrophotographic process.
A novel method for forming an image according to the present invention includes the steps of transferring the image data generated from a reading device to an image memory switching device, transferring the image data generated from an external function to the image memory switching device, storing the image data in one memory device, switching among the plurality of memory devices, storing the image data in the memory device switched among the plurality of memory devices, and outputting the image data or different image data stored in an image memory in one of the plurality of memory devices to a recording device.